Hydraulic control linkage for implement

ABSTRACT

A hydraulic circuit or linkage system for controlling the attitude of an implement relative to a fixed support while the implement is being raised and lowered relative to the support. The implement is pivoted on one end of a boom by a fluid ram having pressurized fluid supplied thereto through a control valve. The hydraulic control linkage includes a master piston and cylinder assembly interposed between the implement and the support with a slave piston cooperating with the valve spool of the control valve and slidable in a slave cylinder. The opposite ends of the two cylinders are interconnected so that the slave piston is moved in response to movement of the master piston to automatically maintain the predetermined attitude of the implement relative to a fixed reference plane. The hydraulic control linkage further includes mechanism for automatically stopping the bucket at a desired angular relation while it is moving between a first and a second maximum pivoted position and automatically preventing the movement of the bucket beyond the second maximum pivoted position. This is accomplished through a valve having a plurality of flow paths between the conduits interconnecting opposite ends of the two cylinders.

United States. Patent 1151 3,695,474 Blakely 1 Oct. 3, 1972 [54]HYDRAULIC CONTROL LINKAGE FOR [57] ABSTRACT IMPLEMENT A hydrauliccircuit or linkage system for controlling [72] Inventor: Richard P.Blakely, Rockford, Ill. the attitude of an implement relative to a fixedsupport while the implement is being raised and lowered [73] Asslgnee'Case Company relative to the support. The implement is pivoted on [22]Filed: Aug. 5, 1970 one end of a boom by a fluid ram having pressurizedfluid supplied thereto through a control valve. The Appl' 61359hydraulic control linkage includes a master piston and cylinder assemblyinterposed between the implement [52] 1.8. CI. ..214/77l, 214/764,214/763 a d th s port with a slave piston cooperating with Clthe valvespool of the ontrol alve and slidable in a Field of Search 214/140, 762,771, slave cylinder. The opposite ends of the two cylinders 214/779, 1764 are interconnected so that the slave piston is moved in response tomovement of the master piston to auto- References C'ted maticallymaintain the predetermined attitude of the implement relative to a fixedreference plane. The UNITED STATES PATENTS hydraulic control linkagefurther includes mechanism 3,410,433 11/1968 Brown ..2l4/763 f t ti llstopping the bucket at a desired an- Kampert gular relation it is movingbetween a first and a 2,914,202 11/1959 Wag er ..2l4/763 sec nd maximumpivoted position and automatically 3,429,471 2/1969 Austln et al...2l4/763 preventing the movement f the bucket beyond the 2,883,0774/1959 Pilch ..2l4/763 Primary ExaminerGerald M. Forlenza AssistantExaminerJohn Mannix Attorney-Dressler, Goldsmith, Clement & Gordonsecond maximum pivoted position. This is accomplished through a valvehaving a plurality of flow paths between the conduits interconnectingopposite ends of the two cylinders.

21 Claims, 5 Drawing Figures PATENTEDncr 3 m2 SHEET 1 OF 2 P hard/NVEN7102 R. Z

P Elake 6% PATENTEU 3 I97? 3 695,474

sum 2 or 2 FIGA HYDRAULIC CONTROL LINKAGE FOR IMPLEMENT BACKGROUND OFTHE INVENTION The present invention relates to the vehicle supportedimplements and more particularly to a control system which automaticallypositions an implement in any or one of a plurality of predeterminedangular positions relative to a fixed reference plane.

In a typical construction of a vehicle mounted implement, the vehicle,such as a tractor, provides a support or base which has one end of aboom structure mounted for pivotal swinging movement, normallyaccomplished through hydraulically powered means. The opposite end ofthe boom structure supports an implement, such as a tilting bucket,which is normally pivoted thereon through a fluid ram or power means. Inthe normal operation of such a vehicle, the boom structure is moved to alowered position, and the implement is moved to an angular position forengaging material as the tractor is driven forwardly to locate thematerial within the bucket. Thereafter, the boom is raised to carry theimplement and the material to a height enabling dumping of the implementso as to transfer the material to another vehicle or to some otherlocation.

In order to increase the efficiency of operation of a vehicle supportedimplement of this type, various types of automatic controls have beenproposed so that the operator may attend to other necessary functionswhile the implement is being repositioned on the boom. For example,various types of linkages have been proposed for maintaining theimplement at a level condition as the boom is moved between lowered andraised positions, which are often referred to as self-leveling controls.Other types of mechanisms have been proposed for automatically stoppingthe implement at a predetermined angle relative to a reference planeafter the material has been dumped at the subsequent location, which isusually referred to as the return-to-dig position. Still further deviceshave been proposed for preventing the pivoting of the implement beyond amaximum angular relation relative to a reference plane to prevent thedumping of the material onto the operator or the vehicle, commonlycalled the anti-rollback position. However to date no satisfactorysingle control unit has been proposed for performing all of the abovefunctions without the necessity of providing mechanical connectionsbetween relatively movable elements of the material handling device.

SUMMARY OF THE INVENTION The present invention contemplates the simpleand effective hydraulic linkage interposed between the support, theimplement and the control valve which supplies fluid to and from thefluid ram moving the implement relative to the support. The hydrauliclinkage is capable of automatically (1) maintaining the implement at alevel position while the implement is being raised and lowered relativeto the vehicle; (2) automatically preventing movement of the implementbeyond a maximum position; and (3) automatically returning the implementto a working position, after the material has been dumped. All of theabove is accomplished without a mechanical connection between thesupport, implement and control valve. The hydraulic linkage includes amaster piston and cylinder assembly, a slave piston and cylinderassembly and flexible conduits and a control valve interposed betweenthe two assemblies.

More specifically, the present invention contemplates a master pistonand cylinder fluid assembly having elements respectively connected to asupport and an implement with the implement being pivoted onthe supportby a boom. The slave cylinder and piston assembly cooperates with avalve spool that is actuated to supply pressured fluid to a fluid motorwhich pivots the implement on the outer end of the boom. The twocylinders are interconnected by a pair of conduits having fluid thereinso that movement of the implement toward and away from the support willactuate the valve spool and maintain the implement in a level conditionrelative to the vehicle.

A control valve is interposed between the conduit and defines first andsecond flow paths with relief valves in the respective paths andresponsive to a first pressure of the hydraulic fluid in the respectiveconduits to provide flow paths in opposite directions between theconduits thereby accommodating manual actuation of the valve spool toposition the implement at positions other than the level positionrelative to the vehicle.

The hydraulic control linkage further includes means for blocking flowin one of the paths when the implement reaches a first or maximumposition to prevent manual actuation of the valve spool after theimplement reaches the maximum position. In addition, one of the flowpaths is divided into first and second branch paths with a relief valvein each branch path. The relief valve in the second branch path isresponsive to a greater pressure than that in the first branch and thefirst branch path is blocked when the implement reaches a workingposition relative to the support while both branch paths are blockedwhen the implement reaches the maximum position to prevent actuation.

With the hydraulic control linkage or circuit of the present inventioninterposed between an implement, a support and a valve spool controllingthe implement, the implement will automatically be maintained in aleveled condition as the implement is raised and lowered relative to thevehicle. In addition, to position the implement to a working positionfrom a dumped position, the operator need only move the valve spool ofthe control to a detented position and the control linkage willautomatically stop the implement at the working position. Furthermore,the hydraulic control linkage is arranged in a manner that the operatormay manually override the automatic control to move the implement beyondthe working position, after the implement has been filled. withmaterial.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS FIG. 1 shows a vehiclemounted implement having the present invention incorporated. therein;

FIG. 2 is a schematic illustration of the hydraulic control circuit ofthe present invention;

FIG. 3 is a fragmentary schematic illustration of the hydraulic controlcircuit illustrating elements required for performing one function ofthe control;

FIG. 4 is a fragmentary schematic illustration of the control circuitcapable of performing a second function; and

FIG. 5 is schematic illustration of the control circuit for performing athird function.

DETAILED DESCRIPTION While this invention is susceptible of embodimentin many different forms, there is shown in the drawings and will hereinbe described in detail one specific embodiment, with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit theinvention to the embodiment illustrated.

FIG. 1 of the drawings discloses an earthworking implement 10, such asfront end loader of.the articulated type. The loader includes a powersection 12 supported on a pair of wheels 14 (only one being shown) andpivotally connected at one end to a loader support section 16, alsosupported on a pair of wheels 18 (only one being shown). The sections 12and 16 combine to define a vehicle with the section 16 having the loaderstructure supported thereon. The loader structure includes a boom or apair of lift arms 20 (only one being shown) having their adjacent end'spivoted at 22 on a fixed support defined by the section 16. The liftarms 20 are adapted to be raised and lowered through fluid rams 24 (onlyone being shown) pivoted at one end on the section or support 16 andrespectively connected at the opposite end to the lift arms by pivotpins spaced from the pivot pins 22.

An implement or bucket 28 is pivotally supported at 30 adjacent to thefree end of the lift arms and is adapted to be pivoted between first andsecond positions through hydraulically operated linkage mechanism 32,which will now be described.

A hydraulically actuated linking mechanism consists of a compoundlinkage including links 34 and 36 pivotally interconnected at one end,with the link 34 being pivoted on the bucket 28 at a location spacedfrom the pivot pin 30 while the free end of the link-36 is pivoted at 40on the lift arms or boom, also at a location spaced from the pivot pin30. While two such linkages are included, only one has been shown forpurposes of illustration.

The hydraulically operated linkage mechanism further includes fluid rams42 (only one being shown) each consisting of a cylinder 44 and a pistonrod 46 with the cylinder being trunion mounted at 48 on the link 36while the piston rod 46 is pivotally supported on the boom at 50. Thus,portions of the lift arms 20 and the bucket 28 cooperate with the link34 and 36 to define a parallel linkage system, the configuration ofwhich is changed by extension and retraction of the piston rods relativeto the cylinders to move the bucket between the first and secondpositions.

To extend and retract the piston rods, the hydraulic means furtherincludes a reservoir 60, a pump 62 and a control valve 64. The controlvalve is connected to the reservoir through a conduit 66 while the pump62, the reservoir 60 and the valve 64 are interconnected through aconduit 68. Thus, movement of the valve spool 74 in opposite directionsfrom a neutral position will placexthe respective conduits 66 and 68 incommunication with conduits 70 and 72 connected to opposite ends of thecylinders 44.

The control valve 64 may be of a commercially available type in whichthe valve spool 74 is biased to a neutral position within a housing 76and actuated by a manual control lever 78 connected to the valve spoolthrough a linkage 79. Since all of these elements are of thecommercially available type, no detailed description thereof is to benecessary.

According to the present invention, a hydraulic control circuit orlinkage means is interposed between the valve spool 74, the section orsupport 16 and the implement 28 and is capable of automaticallymaintaining the implement at a predetermined angle relative to a fixedreferenced plane during raising of the boom; preventing movement of theimplement beyond a first maximum angle relative to a fixed referencedplane; and returning the implement to a desired angle relative to thefixed referenced plane after the implement has been moved to a secondmaximum angle. All of the above is accomplished by the use of a minimumnumber of parts and the use of hydraulic fluid as a linkage between acontrol valve spool and the implement allows for the use of flexiblehosing to eliminate the need for mechanical connections between thevarious elements.

According to the present invention, the hydraulic circuit or linkageincludes a piston rod and cylinder assembly having its first element orcylinder 92 pivotally connected to the support 16 and its second elementor piston rod 94 pivotally connected to the implement or bucket 28. Inthe illustrated embodiment, the piston rod 94 is connected to the bucket28 through the parallelogram linkage 34, 36. However, the piston rodcould readily be connected directly to the bucket 28 and may beconsidered as such for the purposes of the present invention.

The hydraulic circuit of the present invention further includes a slavecylinder and piston assembly or arrangement having a cylinder 102attached directly to the valve housing 76 to define a chamber adjacentthe valve spool 74. A piston 104 is slidably disposed within the chamber102 and is connected to move with the valve spool 74 through anextension or rod 106.

Opposite ends of the master cylinder 92 and the slave cylinder 102 areinterconnected by a pair of conduits 108 and 110. Thus, with anincompressible fluid, such as oil, in the conduits 108 and 110 as wellas the cylinders 92 and 102, pivotal movement of the implement or bucket28 toward and away from a support 16 forming part of the vehicle, willmove the piston 104 and the valve spool 74 in appropriate directions inresponse to movement of the piston or element 94a by transmitting fluidthrough either of the conduits 108 or 110 and automatically maintain thebucket at a predetermined angular relationship relative to a fixedreferenced plane.

According to a further aspect of the present invention, thepredetermined angular relationship relative to the fixed referencedplane, can readily be set by the operator of the vehicle. For thispurpose, the hydraulic circuit of the present invention further includesvalve means between the conduits 108 and 110 and defining first andsecond flow paths with relief valves in each of the paths. The reliefvalves are responsive to a first pressure of the hydraulic fluid in theclosed circuit between the cylinders 92 and 102 and are capable of beingopened by supplying a pressure to the fluid through the manual controllever 78 and the valve spool 74. This arrangement allows for flow in theopposite directions between the two conduits to accommodate manualactuation of the valve spool. Stated another way, the valve means allowsthe valve spool 74 and the piston 104 to remain in a manually actuatedposition by accommodating relative movement of the elements 92 and 94while the slave piston 104 is in a fixed position.

The control valve 116 for accomplishing the above incorporates first andsecond flow paths 118 and 120 interconnecting the respective conduitswith the first flow path 1 18 having biased valve means or a pressureresponsive relief valve 122 in the path limiting flow of fluidtherethrough in a direction from the conduit 110 to the conduit 108.Likewise, the second flow path 120 has biased valve means or a pressureresponsive relief valve 124 normally blocking flow through the flow pathand limiting the flow of fluid from conduit 108 to conduit 110.

The relief valves 122 and 124 are adapted to be opened when the pressureof the fluid in the closed hydraulic system defined by the cylinders 92and 104 and the conduits 108 and 110 exceeds a first pressure level.This pressure level is relatively low so that a small amount of manualforce applied to the control lever 78 in either direction from itsneutral position will increase the pressure of the fluid in theappropriate conduits 108 or 110 and open the respective relief valves122 or 124. With such an arrangement the opening of the relief valvesand holding the control in an actuated position will allow the operatorto override the automatic control described above and to hold the valvespool 74 and piston 104 in a fixed position while the appropriate reliefvalves 122 and 124 will accommodate flow of fluid between the conduits108 and 110 and allow relative movement of the element 92 and 94 of themaster fluid ram 90.

As was indicated above, the hydraulic circuit also includes means forautomatically preventing movement of the implement beyond a firstmaximum angle relative to the fixed referenced plane and forautomatically returning the implement to a predetermined desired anglerelative to said referenced plane after the implement has been moved toa second maximum angle. With particular reference to a bucket, the firstmaximum angle or position described above, may be defined as theanti-rollback" angle beyond-which the bucket should not be tilted; andthe predetermined desired angle would generally be considered theworking or return-to-dig angle or position for the bucket.

For this purpose, the second flow path 120 has first and second branchpaths 120a and lb with branch path 120a having the relief valve 124disposed therein while the branch path 120b has a further relief valveor biased valve means 126 disposed therein. The relief valve 126 isresponsive to being opened at a second pressure which is greater thanthe pressure required for opening valve 124, as will be described later.

In addition, the control valve spool 74 has a detented position formoving the implement or bucket from the dumped or first position to themaximum rollback or second position. Such mechanism may be incorporateddirectly within the valve, as is well-known in the art and will beschematically described in connection with FIG. 2. Thus, the valve spoolhas a further extension 130 thereon with a groove or recess 132 in theextension. A pawl or detent 134 is biased into engagement with theextension 130 by a compression spring 136 so that the end of the pawlwill be received in the groove 132 and hold the valve 74 in a detentedoperative position. The pressure of the fluid required in the closedloop fluid circuit to overcome the force of the spring 136 is less thanthe pressure of the fluid required to open the relief valve 126, for apurpose which will be described. While the detent mechanism has beenschematically illustrated externally of the valve 64 it may readily beand usually is incorporated within the housing.

The hydraulic control circuit further includes means for blocking theflow through the first branch 120a of the flow path 120 when theimplement is pivoted to an intermediate angle between the first andsecond maximum angles. In the illustrated embodiment, the means forblocking flow includes a sleeve 140 carried by an extension 142extending from one side of the piston 940 while the first branch path120a communicates with the conduit through one end of the cylinder 94.

Thus, as the bucket is being rolled back or pivotally moved from thesecond or dumped position, through actuation of the manual control lever78 to the right as viewed in FIG. 2, the sleeve will eventually becomealigned with the port 144 connecting the branch path a to the cylinder92 to thereby block flow of fluid through the branch path.

Normally, the manual control lever will be moved sufficiently to placethe detent 134 into the groove 132 and the control valve spool 74 willthereby be maintained in an actuated position. However, by setting thepressure required for opening relief valve 126 at a level higher thanthat required for overcoming spring 136, the blocking of the branch portor branch path 120a will cause an increase in pressure of the fluid inthe closed circuit to move the valve spool 74 from its detented to itsneutral position. .Alternatively, if the operator happens to be manuallyholding the valve spool in an actuated position for moving the bucketfrom the dumped to the roll-bac.k position, blocking of the port 144will cause a pressure increase in the system sufficient to beanindicator to the operator that the implement is at the desiredintermediate position and he can thereby immediately release the controllever. Of course, release of the control lever will cause theself-centering spool of the control valve to move to its neutralposition.

Additionally, by providing the two branch paths with the respectiverelief valves 124 and 126 at different pressure settings, the operatormay manually override the intermediate or return-to-dig position byapplying a sufiicient pressure to the control system (by movement of thecontrol lever in a clockwise direction as used in FIG. 2) to open therelief valve 126 and accommodate further pivotal movement from theintermediate position of the implement toward the second maximumposition of the implement. After the initial pivotal movement of theimplement toward the support or vehicle, the port 144 will be opened toallow further flow of fluid through branch conduit 120a.

According to a further aspect of the present invention, both of thebranch paths 120a and 120b are blocked when the implement reaches thefirst maximum position to prevent any further manual control oractuation of the valve 74 in a direction to allow movement of theimplement beyond the first maximum position. The means for accomplishingthe above includes the specific location of the port 144 connectingbranch path 120a to the cylinder 92 and a location of a second port 146between the rod end side of cylinder 92 and the port 144. Thus, the port146 will first become blocked by the piston 94a, but at this point,nothing will occur since the conduit 108 is still adapted to beconnected to the conduit 110 through the first branch 120a of the secondflow path 120. However, with the port 144 connecting branch path 120a tothe cylinder 92 located so that the piston 94a will block the port 144when the implement reaches the first maximum position, the fluid inconduit 108 and the respective ends of the cylinders 92 and 102 istrapped and the incompressibility of the fluid prevents the manualcontrol lever to be moved to actuate the valve spool to the rollbackposition.

According to a further aspect of the present invention, the hydrauliccircuit further includes means for supplying additional fluid to theclosed system whenever required. For this purpose, the flow path 120 isconnected through a conduit 150 to a source of fluid 152 and the flowpath has a further check valve 154 disposed therein which has arelatively low setting. With this arrangement the fluid in the source152 will constantly replenish any loss of fluid within the closedcircuit including the conduits 108,110, the master cylinder 92, theslave cylinder 102 and the control valve with its associated flowpassages. If desired the master cylinder and piston assembly 90 mayfurther include a sight indicator 160 for visually indicating theapproximate position of the implement relative to the bucket. The sightindicator could include a suitable indicating device 162 and have theextension 142 extending through the head end of the cylinder 92 with theposition of the bucket thereby automatically being indicated by themovement of the extension.

The operation of the hydraulic control circuit of the present inventionwill be described in connection with each individual function performedby the control circuit, with particular reference to FIGS. 3-5. FIG. 3shows the components for maintaining the implement or bucket in a fixedangular relation to a reference plane while the implement is beingraised and lowered relative to the vehicle (self-leveling). Assumingthat no fluid is being directed to the implement ram 42 and fluid isbeing directed to the head end of fluid ram 24, the boom will be raisedand the fixed relationship of the parellelogram linkage will cause thebucket to be tilted rearwardly as the boom is being raised. This willcause a movement of the pivotal connection 48 toward the support andmove piston 94a within cylinder 92. The relative movement of theelements 94a and 92 will force fluid trapped within the closed loop tobe diverted from the head end of cylinder 92 to the corresponding end ofcylinder 102 thereby moving piston 104 and the valve spool toward thedump position to supply pressure fluid to the head end of cylinder 44.This movement will continue until the bucket is at the predeterminedangular relationship. It should be noted that this will occur eventhough the valve spool 74 is biased to a neutral position because thepressure required to overcome the bias on the spool is less than thepressure required to open relief valves 122 and 124.

Of course, movement of the boom in the opposite direction, would movethe valve spool toward the rollback position and again automaticallymaintain the implement or bucket at a leveled condition.

At any time during the movement of the bucket, the operator may manuallyoverride the automatic leveling control by mere actuation of the controllever 78. Such actuation will produce a sufficient force to open eitherof relief valves 122 or 124, dependent upon the direction of movement ofspool 74 to allow the operator to reset the position of control. It willbe appreciated that the operator may set any desired position of controlbetween the first and second maximum or rollback and dump positions forthe implement by mere manipulation of the manual lever. Once the position has been established, the operator need only release the controllever and self-centering spool 74 will move to its neutral position.Thereafter, the an gular position of the implement or bucket when thevalve reaches neutral will be maintained while the boom or left arms 20are being raised and lowered.

The theory of preventing the implement from moving beyond a firstmaximum angle relative to a fixed referenced plane will be described inconnection with FIG. 4. The illustrated elements necessary forpreventing the bucket from moving beyond the maximum rollback positionare shown in FIG. 4 where it will be noted that the flow path 120 isshown as communicating with the conduit 108 through a port 144 adjacentthe head end of the cylinder 92. Assuming that the manual control 78 hasbeen moved to place the valve spool 74 to the rollback position, whenthe implement reaches the maximum rollback angle, the piston 94a will bein axial alignment with the port 144 and will block the port to lock theelements 94, 94a and 92 of the fluid ram relatively to each other toprevent any further manual control. As was indicated above, once theflow path is blocked, the fluid in conduit 108 and the associated endsof the cylinder 104 and 92 is trapped to prevent actuation of thecontrol valve spool 74 to the rollback position.

The operation of automatically returning the implement to a workingposition or more specifically, the bucket to a return-to-dig position isshown in FIG. 5. During normal operation of the implement, after thebucket has been dumped the operator generally moves the valve spool 74to a detented rollback position so that he may release the control leverand direct his attentions to other functions which are required to beperformed. Thus, as the implement is being pivoted or tilted from thesecond maximum position toward the first maximum position, the pistonrod 94 will be retracting within the cylinder 92 and the sleeve 140,being fixed to the extension 142 will likewise be moving toward the headend of the cylinder. When the sleeve is in axially alignment with theport 144, the flow of fluid from conduit 108 to conduit 110 isinterrupted. Thus, by having the spring force on relief valve 124 lowerthan the spring force on the detent 134 and the spring force on reliefvalve 126 higher than that on detent 134, the pressure in conduit 108will increase and will be sufficient to release the detent 134 and allowthe self-centering valve spool 74 to move to the neutral position.However, the branch path 12% will still allow the operator to manuallyoverride the control mechanism by applying a sufficient force to controllever 70 to open relief valve 126. Also, as was indicated above, if theoperator should be holding the control lever 78 rather than having thevalve spool in its detented position, the blocking of the port 144 willincrease the pressure in the conduit 108 and this pressure will betransmitted through the control valve spool 74 to the control lever toact as an indicator to the operator that the implement is at the workingor return-todig position.

lt should be noted at this point while the means for blocking flowbetween the conduits to stop the implement at its working position andto prevent movement of the implement beyond a maximum position, havebeen shown as being incorporated into the cylinder and piston rodassembly 90, it will readily be appreciated that various mechanismscould be utilized for blocking the flow in the respective flow paths120a and 12%. For example, the two flow paths could be placed directlybetween the conduits and suitable pressure responsive mechanism could beplaced in the respective flow paths to close the flow paths when thepressure reaches the desired level. However, for purposes of simplicity,the illustrated embodiment of the control valve 116 shown in FIG. 2,considerably simplifies the number of components required forsimultaneously performing the three desired functions. Thus, by properarrangement of the ports 144 and 146, the port 144 can be blocked bysleeve 140 to stop the implement at its working position, while thepiston 940 may be utilized for simultaneously blocking both ports 144and 146 when the implement reaches the first maximum angle.

The vehicle as well as the particular hydraulic linkage mechanism shownin FIG. 1 has been illustrated merely for purposes of illustration andis not considered to be limited to the elements described. For example,the hydraulic control linkage 32 could readily be a fluid ram interposeddirectly between the boom and the bucket 28. Also, the vehicle 10 neednot be of the articulated type.

As can be seen from the above description, the present inventionprovides a simple and effective hydraulic control linkage forautomatically controlling the position of the control valve andsimultaneously performing a plurality of functions. The componentsrequired are inexpensive and easily incorporated into existingearthworking devices. The arrangement allows for the elimination of anydirect mechanical connection between the relatively movable implementand the relatively fixed valve. To reiterate, the connection between theimplement and the valve is in the form of flexible hosing whicheliminates the need for mechanical linkage heretofore required forcontrols of this type.

What is claimed is:

l. A material handling device comprising a vehicle having one end of aboom pivotally supported thereon with a material handling implementmovable on the opposite end of said boom; hydraulic means for movingsaid implement on said boom and including a fluid motor havingrelatively movable elements, respectively, connected to the boom and theimplement; said hydraulic means further including a fluid source underpressure, a reservoir, a valve and conduit means interconnecting saidvalve, motor, source and reservoir; said valve having a spool slidablein a chamber and movable in opposite directions from a neutral positionto move said implement in opposite directions on said boom, theimprovement of a hydraulic control linkage means interposed between saidspool and said implement for causing actuation of the spool andconsequently l) maintaining said implement at a predetermined anglerelative to a fixed reference plane during raising of said boom (2)preventing movement of said implement beyond'a first maximum anglerelative to said reference plane; and (3) returning'said implement to adesired angle relative said reference plane after said implement hasbeen moved to a second maximum angle.

2. Amaterial handling device as defined in claim 1, in which saidhydraulic control linkage means further includes means defining achamber adjacent said spool; a slave piston slidable in said chamber andconnected to said spool; a piston rod and cylinder assembly havingelements respectively connected to said vehicle and said implement andconduit means: connecting opposite ends of said cylinder to oppositeends of said chamber with hydraulic fluid in said conduit means, saidcylinder and said chamber whereby relative movement between saidelements will actuate said valve.

3. A material handling device as defined in claim 2, in which saidhydraulic means includes manual means for moving said valve spool, thefurther improvement of means in said hydraulic control linkage means forallowing said valve spool to remain in a manually actuated position byaccommodating movement of said elements while said slave piston is in afixed position.

4. A material handling device as defined in claim 3, including thefurther improvement of mechanism in said hydraulic control linkage meansfor locking said elements relative to each other when said implement isat said first maximum angle.

5. A material handling device as defined in claim 4, including biasingmeans normally maintaining said valve spool in a neutral position andbiased detent means maintaining said valve spool in an actuated positionfor moving said implement from said second maximum angle toward saidfirst maximum angle; the further improvement of means in said hydrauliccontrol linkage means for returning said valve spool to said neutralposition when said implement reaches said desired angle.

6. A material handling device as defined in claim 2, in which saidconduit means includes first and second conduits having opposite endsrespectively connected to opposite ends of said cylinder and saidchamber, the furtherimpro'vement of a flow control valve defining firstand second unidirectional flow paths in opposite directions and biasedvalve means in said flow paths normally blocking flow through said flowpaths, said valve means accommodating flow in opposite directionsbetween said conduits upon manual actuation of said valve spool inopposite directions from said neutral position.

7. A material handling device as defined in claim 6, the furtherimprovement of mechanism for blocking flow through one of said flowpaths when said implement reaches said first maximum angle.

8. A material handling device as defined in claim 6, in which saidsecond flow path includes first and second parallel branch paths betweensaid conduits,

each having biased valve means therein; means for blocking flow throughsaid first branch path when said implement reaches said desired angle toreturn said valve spool to said neutral position, said second branchpath accommodating flow between said conduits upon subsequent manualactuation of said valve spool; and means blocking both branch paths whensaid implement reaches said first maximum angle.

9. In a vehicle having a boom pivoted on a suppo between raised andlowered positions, an implement pivoted on said boom, power means forpivoting said implement on said support between first and secondpositions, a control valve having a self-centering spool movable inopposite directions from a neutral position to direct fluid to and fromsaid power means and pivot said implement, the improvement of separatehydraulic linkage means between said support, said implement and saidvalve spool for automatically moving said spool to any one of saidpositions and maintain said implement at a predetermined angle relativeto a fixed reference plane during raising and lowering of said boom,said hydraulic linkage means including means for preventing actuation ofsaid valve spool when said implement reaches said second position.

10. A vehicle as defined in claim 9, in which said hydraulic linkagemeans includes a slave cylinder and slave piston cooperating with saidspool, and means interposed between said support and said implement formoving said slave piston in said slave cylinder in response to movementof said implement relative to said support.

11. A vehicle as defined in claim 10, in .which said last means includesa master cylinder connected to said support and a master pistonconnected to connected implement; and conduits interconnecting oppositeends of said cylinders.

12. A vehicle as defined in claim 9, in which said hydraulic linkagemeans includes an assembly having cylinder and piston elementsrespectively connected to said support and said implement and meansoperatively connecting opposite ends of said cylinder element to saidspool to move said spool in response to movement of said piston elementrelative to said cylinder element.

13. A vehicle as defined in claim 9, in which said hydraulic linkagemeans includes a master cylinder having a master piston slidable thereinand interposed between said support and said implement; a slave cylinderhaving a piston slidable therein and connected to said spool; and firstand second conduits connecting opposite ends of said cylinders, saidconduits defining first and second closed fluid paths between oppositeends of the respective pistons.

14. A vehicle as defined in claim 13, including the further improvementof valve means interposed between said fluid paths and operative uponmanual actuation of said spool in opposite directions from a neutralposition to allow independent movement of said bottom.

15. A vehicle as defined in claim 14, in which said valve means definesfirst and second normally closed flow paths between said fluid paths andbiased means in said flow paths responsive to manual movement of saidspool to open said flow paths.

16. A vehicle as defined in claim 15, in which one of said flow pathshasfirst and second parallel branch paths, each having valves normallyblocking flow therein, said valves respectively being responsive tofirst and second pressures of fluid in one of said fluid paths, toconnect said one of said fluid paths with the other fluid path.

17. In combination with a vehicle having one end of a boom pivotedthereon and an implement pivoted on the opposite end of the boom betweenfirst and second positions by a fluid motor supplied with fluid througha valve having a spool biased to a neutral position, a hydraulic controllinkage interposed between the vehicle, implement and valve spool andcomprising a master piston and cylinder assembly having elementsrespectively connected to the vehicle and implement; a slave piston andcylinder assembly cooperating with said valve spool; and first andsecond conduits interconnecting respective ends of said cylinderelements and having hydraulic fluid therein whereby movement of saidimplement toward and away from said vehicle will actuate said valve inopposite directions from said neutral position to maintain saidimplement in a level position relative to said vehicle while the boom israised and lowered on the vehicle.

18. The combination as defined in claim 17, the further improvement ofvalve means between said conduits defining first and second flow pathsbetween said conduits with relief valves in said paths and responsive toa first pressure of said hydraulic fluid in said respective conduits toprovide flow in opposite directions between said conduits to accommodatemanual actuation of said valve spool.

19. The combination as defined in claim 18, including the furtherimprovement of means for blocking flow in one of said paths when saidimplement reaches said first position to prevent manual actuation ofsaid valve spool.

20. The combination as defined in claim 18, including the furtherimprovement of one of said flow paths having first and second branchpaths with said relief valve of said flow path located in said firstbranch path, a further relief valve in said second branch path and beingresponsive to a second pressure greater than said first pressure; andmeans for blocking flow in said first branch path to position saidimplement in an intermediate position between said second and levelpositions, said further relief valve accommodating flow between saidconduits upon subsequent manual actuation of said spool to accommodatemovement of said implement from said intermediate position to said firstposition.

21. The combination as defined in claim 20, including the furtherimprovement of means blocking flow in both branch paths when theimplement reaches said first position to prevent manual actuation ofsaid valve spool for movement beyond said second position.

1. A material handling device comprising a vehicle having one end of aboom pivotally supported thereon with a material handling implementmovable on the opposite end of said boom; hydraulic means for movingsaid implement on said boom and including a fluid motor havingrelatively movable elements, respectively, connected to the boom and theimplement; said hydraulic means further including a fluid source underpressure, a reservoir, a valve and conduit means interconnecting saidvalvE, motor, source and reservoir; said valve having a spool slidablein a chamber and movable in opposite directions from a neutral positionto move said implement in opposite directions on said boom, theimprovement of a hydraulic control linkage means interposed between saidspool and said implement for causing actuation of the spool andconsequently (1) maintaining said implement at a predetermined anglerelative to a fixed reference plane during raising of said boom; (2)preventing movement of said implement beyond a first maximum anglerelative to said reference plane; and (3) returning said implement to adesired angle relative said reference plane after said implement hasbeen moved to a second maximum angle.
 2. A material handling device asdefined in claim 1, in which said hydraulic control linkage meansfurther includes means defining a chamber adjacent said spool; a slavepiston slidable in said chamber and connected to said spool; a pistonrod and cylinder assembly having elements respectively connected to saidvehicle and said implement and conduit means connecting opposite ends ofsaid cylinder to opposite ends of said chamber with hydraulic fluid insaid conduit means, said cylinder and said chamber whereby relativemovement between said elements will actuate said valve.
 3. A materialhandling device as defined in claim 2, in which said hydraulic meansincludes manual means for moving said valve spool, the furtherimprovement of means in said hydraulic control linkage means forallowing said valve spool to remain in a manually actuated position byaccommodating movement of said elements while said slave piston is in afixed position.
 4. A material handling device as defined in claim 3,including the further improvement of mechanism in said hydraulic controllinkage means for locking said elements relative to each other when saidimplement is at said first maximum angle.
 5. A material handling deviceas defined in claim 4, including biasing means normally maintaining saidvalve spool in a neutral position and biased detent means maintainingsaid valve spool in an actuated position for moving said implement fromsaid second maximum angle toward said first maximum angle; the furtherimprovement of means in said hydraulic control linkage means forreturning said valve spool to said neutral position when said implementreaches said desired angle.
 6. A material handling device as defined inclaim 2, in which said conduit means includes first and second conduitshaving opposite ends respectively connected to opposite ends of saidcylinder and said chamber, the further improvement of a flow controlvalve defining first and second unidirectional flow paths in oppositedirections and biased valve means in said flow paths normally blockingflow through said flow paths, said valve means accommodating flow inopposite directions between said conduits upon manual actuation of saidvalve spool in opposite directions from said neutral position.
 7. Amaterial handling device as defined in claim 6, the further improvementof mechanism for blocking flow through one of said flow paths when saidimplement reaches said first maximum angle.
 8. A material handlingdevice as defined in claim 6, in which said second flow path includesfirst and second parallel branch paths between said conduits, eachhaving biased valve means therein; means for blocking flow through saidfirst branch path when said implement reaches said desired angle toreturn said valve spool to said neutral position, said second branchpath accommodating flow between said conduits upon subsequent manualactuation of said valve spool; and means blocking both branch paths whensaid implement reaches said first maximum angle.
 9. In a vehicle havinga boom pivoted on a support between raised and lowered positions, animplement pivoted on said boom, power means for pivoting said implementon said support between first and second positions, a control valvehaving a self-centering spool moVable in opposite directions from aneutral position to direct fluid to and from said power means and pivotsaid implement, the improvement of separate hydraulic linkage meansbetween said support, said implement and said valve spool forautomatically moving said spool to any one of said positions andmaintain said implement at a predetermined angle relative to a fixedreference plane during raising and lowering of said boom, said hydrauliclinkage means including means for preventing actuation of said valvespool when said implement reaches said second position.
 10. A vehicle asdefined in claim 9, in which said hydraulic linkage means includes aslave cylinder and slave piston cooperating with said spool, and meansinterposed between said support and said implement for moving said slavepiston in said slave cylinder in response to movement of said implementrelative to said support.
 11. A vehicle as defined in claim 10, in whichsaid last means includes a master cylinder connected to said support anda master piston connected to connected implement; and conduitsinterconnecting opposite ends of said cylinders.
 12. A vehicle asdefined in claim 9, in which said hydraulic linkage means includes anassembly having cylinder and piston elements respectively connected tosaid support and said implement and means operatively connectingopposite ends of said cylinder element to said spool to move said spoolin response to movement of said piston element relative to said cylinderelement.
 13. A vehicle as defined in claim 9, in which said hydrauliclinkage means includes a master cylinder having a master piston slidabletherein and interposed between said support and said implement; a slavecylinder having a piston slidable therein and connected to said spool;and first and second conduits connecting opposite ends of saidcylinders, said conduits defining first and second closed fluid pathsbetween opposite ends of the respective pistons.
 14. A vehicle asdefined in claim 13, including the further improvement of valve meansinterposed between said fluid paths and operative upon manual actuationof said spool in opposite directions from a neutral position to allowindependent movement of said bottom.
 15. A vehicle as defined in claim14, in which said valve means defines first and second normally closedflow paths between said fluid paths and biased means in said flow pathsresponsive to manual movement of said spool to open said flow paths. 16.A vehicle as defined in claim 15, in which one of said flow paths hasfirst and second parallel branch paths, each having valves normallyblocking flow therein, said valves respectively being responsive tofirst and second pressures of fluid in one of said fluid paths, toconnect said one of said fluid paths with the other fluid path.
 17. Incombination with a vehicle having one end of a boom pivoted thereon andan implement pivoted on the opposite end of the boom between first andsecond positions by a fluid motor supplied with fluid through a valvehaving a spool biased to a neutral position, a hydraulic control linkageinterposed between the vehicle, implement and valve spool and comprisinga master piston and cylinder assembly having elements respectivelyconnected to the vehicle and implement; a slave piston and cylinderassembly cooperating with said valve spool; and first and secondconduits interconnecting respective ends of said cylinder elements andhaving hydraulic fluid therein whereby movement of said implement towardand away from said vehicle will actuate said valve in oppositedirections from said neutral position to maintain said implement in alevel position relative to said vehicle while the boom is raised andlowered on the vehicle.
 18. The combination as defined in claim 17, thefurther improvement of valve means between said conduits defining firstand second flow paths between said conduits with relief valves in saidpaths and responsive to a first pressure of said hydraulic fluid in saidrespective conduits to provide flow in opposite directions between saidconduits to accommodate manual actuation of said valve spool.
 19. Thecombination as defined in claim 18, including the further improvement ofmeans for blocking flow in one of said paths when said implement reachessaid first position to prevent manual actuation of said valve spool. 20.The combination as defined in claim 18, including the furtherimprovement of one of said flow paths having first and second branchpaths with said relief valve of said flow path located in said firstbranch path, a further relief valve in said second branch path and beingresponsive to a second pressure greater than said first pressure; andmeans for blocking flow in said first branch path to position saidimplement in an intermediate position between said second and levelpositions, said further relief valve accommodating flow between saidconduits upon subsequent manual actuation of said spool to accommodatemovement of said implement from said intermediate position to said firstposition.
 21. The combination as defined in claim 20, including thefurther improvement of means blocking flow in both branch paths when theimplement reaches said first position to prevent manual actuation ofsaid valve spool for movement beyond said second position.